The present invention relates to tilt back chairs, and the like, and in particular to a variable back adjustor therefor.
Chairs with tilting backs are well known in the art, particularly in office furniture seating. A chair with an articulated back and seat control is disclosed in copending U.S. patent application Ser. No. 145,854, filed May 1, 1980, entitled SYNCHROTILT CHAIR CONTROL, which is commonly assigned to the present assignee, and is hereby incorporated by reference.
In the above-referenced chair control, the chair back can be locked only in either the fully upright position or the fully reclined position. It is quite advantageous to be able to lock the chair in a wide variety of different angular positions to accommodate various personnel and working environments.
Another problem encountered in the aforementioned chair control is that the articulated back and seat mechanism requires a very strong return spring to insure that the chair normally assumes a fully upright position. Hence, the force acting on the locking mechanism is rather high, thereby requiring a commensurately high force to shift the locking mechanism between the locked and unlocked positions. Although toggle button controllers have a very neat, sleek appearance, heretofore they have not been adapted to transmit substantial shifting forces to the locking mechanism, as are the long lever arrangements which are normally used to lock and unlock the chair back.
Pneumatic and hydraulic seat back adjusters are prone to wear, and are therefore generally not considered to be very reliable.